Sanpete County climate

Sanpete County Frost Dates and Growing Season

NOAA 1991-2020 normals for Ephraim, 2.7 km from Sanpete County, elevation 5498 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ephraim. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 28 and the first fall freeze around September 20, a growing season of about 113 days.

Median at 36°F
last June 13, first September 11
Median at 32°F
last May 28, first September 20
Median at 28°F
last May 12, first September 29

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 29Jun 23Jun 20Jun 17Jun 13Jun 9Jun 6Jun 3May 29
32°FJun 15Jun 8Jun 4Jun 1May 28May 24May 21May 17May 12
28°FMay 31May 23May 19May 16May 12May 9May 6May 2Apr 29
24°FMay 13May 8May 3May 1Apr 29Apr 26Apr 22Apr 18Apr 13
20°FApr 30Apr 25Apr 21Apr 17Apr 13Apr 8Apr 5Mar 31Mar 19
16°FApr 15Apr 7Apr 1Mar 25Mar 19Mar 14Mar 9Mar 5Feb 28

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FAug 28Sep 1Sep 5Sep 8Sep 11Sep 14Sep 17Sep 20Sep 24
32°FSep 5Sep 10Sep 14Sep 17Sep 20Sep 23Sep 25Sep 28Oct 1
28°FSep 15Sep 21Sep 24Sep 27Sep 29Oct 1Oct 4Oct 7Oct 12
24°FSep 25Sep 30Oct 2Oct 6Oct 8Oct 12Oct 16Oct 19Oct 24
20°FOct 5Oct 10Oct 15Oct 18Oct 21Oct 24Oct 28Nov 1Nov 6
16°FOct 17Oct 23Oct 27Oct 31Nov 3Nov 5Nov 9Nov 13Nov 18

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F10810195928883797465
32°F13312712211711310910510093
28°F158150145141137133128122114
24°F183176171166162158154149142
20°F216207201195189184179174166
16°F252242235229224218212205196

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
6,993
Cooling degree days, base 65°F
441
Growing degree days, base 40°F
4,231
Growing degree days, base 45°F
3,165
Growing degree days, base 50°F
2,267
Growing degree days, base 55°F
1,523
Growing degree days, base 60°F
909

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,28600
February98600
March79505
April596033
May3397178
June10459409
July7205663
August17148597
September16922315
October536065
November88702
December1,27200

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 2.7 km from Sanpete County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00422578 (Ephraim). Public domain.